Plug casings having a plurality of contact pins, known as plug boards, must be of water-tight construction on the plug-in side for numerous applications. The contact pins can be secured in the plug board by being pressed in or by injection molding encapsulation. Various steps are known to assure the required sealing properties of the plug boards on the connection side. In the case of contact pins which have been pressed in it is known to provide a plurality of successive truncated cones all oriented with their apices in the direction of pressing in and providing a relatively tight clamping fit in the plastic casing as a result of the resilience of the plastic material. Nevertheless, reliable water-tightness is not always possible to achieve, since the relatively high forces to which plastic parts are subjected may result in continuous ducts being formed.
Another technique for sealing such plugs involves grouting of the contact pins in the casing. For example, a plug board is known in which the contact pins are fitted with clearance. To seal the contact pins, the plug board is grouted with an UV-hardening two-component silicone. This represents an extremely high manufacturing expense, necessitating separate operations. The two-component silicone requires pre-treatment of the plug board by a primer or plasma etching. The liquid silicone is applied by special metering systems and must be hardened in UV-furnaces. The silicone remains liquid in the shadow of the contact pins, which are bent at an angle in many applications. Even if the silicone is subjected to only slight mechanical load, e.g., on movements of the contact pins, the adhesion is lost so that reliable sealing is again impossible to assure.